Spontaneously forming nanostructures: Quantum dot molecules and rings

Annealing molecular beam epitaxy grown Ge/Si(100) islands spontaneously for ms quantum dot molecules and rings. Quantum dot molecules (QDM) are close-p acked arrays of several SiGe alloy hut clusters arranged with rectangular o r circular symmetry. Rings are 3D structures with a depressed center. Both of these structures are related to island ensemble coarsening. Si interdiff usion into the perimeter of nominally pure Ge dome clusters forms a Si-rich annulus surrounding a Ge rich core. This lower melting point core diffuses away during coarsening of the island ensemble leaving behind the QDM. Larg e ring structures are formed by rapid coarsening of large, dislocated clust ers during high temperature anneals. (C) 2001 American Institute of Physics .